Method for forming a plane structure

ABSTRACT

A method for forming a plane structure. It comprises the following steps: forms a liquid material with a thicker thickness on a substrate, rotating both the liquid material and the substrate around the axis of the substrate, applying a solvent on the rotating liquid material to remove partial liquid material. It also comprises the following steps: form a thicker removable material on a substrate, and partially remove the surface part of the removable material.

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/217,471, filed Aug. 14, 2002, which is incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the method for transferring patterns.Specifically, the invnetion is related to the method which effectivelyprevents the defects induced by damaged photoresist during the patterntransferring process.

2. Description of the Prior Art

In some semiconductor fabrications, N-type transistors and P-typetransistors are formed with the following steps in sequence: forms aconductor layer on a substrate, doping numerous impurities into theconductor layer, and patterning the conductor layer. For example, afterthe conductor layer is formed, both the N-type transistor areas and theP-type transistor are doped immediately. For example, after theconductor layer is formed, only the gate area of one type transistor isdoped but the gate area of another type transistor is not doped, suchthat only some transistors have doped gate conductor layer but othertransistors only have undoped gate conductor layer.

Such semiconductor fabrications usually are used to avoid the defects ofthe following processes, while the gates are formed by the patternprocess before the doping process is performed. For example, becauseboth the gates and the substrate are not covered after the patternprocess and before the doping process, it is hard to precisely controlthe doping process to let only the gate conductor layer be doped butboth the source and the drain be not doped, especially being hard toprecisely control the doping process to let only partial gate conductorlayer be doped.

However, such semiconductor fabrications also have the followingdefects:

Although the N-type transistors and the P-type transistors usually usesame material to form their gate conductor layer, the doped density andthe doped impurities often are different between them. Hence, becausedifferent doped materials usually have different etch details, such asetching rate and prefer etch recipe, even they are formed from the sameundoped material, it is hard to precisely form P-type transistors andN-type transistors simultaneously if the doped details of P-typetransistors are different than that of N-type transistors. For example,while the gate area of N-type transistors is doped but the gate area ofthe P-type transistors is not doped, each P-type gate usually is widerthan each N-type gate even their patterns have same width in thecorresponding photo-mask.

Because the substrate must be covered by an anti-reflection layer, suchas a SiON layer, before the exposing process, it is desired to removethe anti-reflection layer after the etching process and then the damagesof formed structures, such as formed gates, often are unavoidable. Forexample, while the phosphoric acid is used to remove the SiON layer, notonly the gate conductor layers are etched by the phosphoric acid butalso different gate conductor layers with different doped details havedifferent etch damages.

It often is desired to perform a thermal treatment before the patterningprocess to re-distribute or diffuse the impurities doped into theconductor layer or the substrate through the conductor layer. Clearly,both the fabrication steps and relative cost are increased.

Moreover, because the etch properties of different materials, such asdoped polysilicon and undoped polysilicon, usually are different, anoptimum etching recipe of one material usually is not effective foranother material. Hence, while different parts of a substrate havedifferent doped properties, it is hard to effectively etch the wholeconductor layer on the whole substrate. Sometimes it is hard to etchdifferent parts in a chamber simultaneously, sometimes it is impossibleto etch different parts at the same time.

Besides, the conductor layer sometimes is not totally smooth, no matteris induced by the existent field oxide before the formation of theconductor layer or is induced by the unavoidable defect(s) of thefabrication of the conductor layer. Hence, the doping result sometimesis not uniform enough. For example, if the conductor layer is thinner onsome parts of the substrate, the doping process for forming the dopedgate conductor layer may also dope some impurities into these parts.Thus, for any transistor located in these parts, not only the gateconductor layer is doped but also both the source and the drain aredoped, which is an unwanted defect.

SUMMARY OF THE INVENTION

One main object of this invention is to improve the conventionaltechnology that patterns the gates before the impurities are doped, suchthat the previous defects induced by the conventional technology thatdopes impurities before the gates be patterned.

Another main object of this invnetion is to provide a method for formingthe plane structure, especially a forming plane structure method whichcould be used to archive the formed object.

One preferred embodiment of the invention is a semiconductorfabrication. Initially, provide a substrate and form both numerous firstgates and numerous second gates on the substrate. Next, form a firstcover layer to cover the substrate, the first gates and the secondgates. Then, form a second cover layer to cover partial substrate, thesecond cover layer only covers the second gates but not covers any firstgate. Sequentially, perform a doping process. Finally, remove bothsecond cover layer and first cover layer.

Another preferred embodiment of the method is a method for forming aplane structure. First, provide a substrate. Then, form a liquidmaterial on the substrate. Finally, remove partial liquid material by aspin-etch process to form a plane structure. Herein, the spin-etchprocess rotates both substrate and liquid material around an axis ofsubstrate and applies a solvent on liquid material to remove partialliquid material simultaneously.

The other preferred embodiment of the invention is a method for forminga plane structure. First, provide a substrate. Next, form a photoresistlayer on the substrate. Then, treat the photoresist layer by apart-expose process such that only the surface part of the photoresistlayer is exposed. Finally, remove exposed part of the photoresist layer.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation and many of the attendant advantages willbe readily obtained as the same becomes better understood by refer enceto the following detailed description when considered in connection withthe accompanying drawings.

FIG. 1A through FIG. 1M qualitatively show the essential steps of onepreferred embodiment of the invention and some available amendments ofthe preferred embodiment;

FIG. 2 shows the essential flow chart of another preferred embodiment ofthe invention; and

FIG. 3 shows the essential flow chart of the other preferred embodimentof the invention

DESCRIPTION OF THE PREFERRED EMBODIMENT

One preferred embodiment of the invention is a semiconductorfabrication. The embodiment at least has the following essential steps:

As shown in FIG. 1A, provide substrate 10 and form numerous first gates11 and numerous second gates 12 on substrate.

As shown in FIG. 1B, cover substrate 10 by first cover layer 13. Herein,first cover layer 13 also covers first gates 11 and second gates 12.

As shown in FIG. 1C, covers partial substrate 10 by second cover layer14. Herein, second cover layer 14 is located over second gates 12 but isnot located over first gates 11.

As shown in FIG. 1D, perform a doping process. Herein, it is possible todope numerous impurities 15 only into first gates 11, it also ispossible to dope impurities 15 into both first gates 11 and partialsubstrate 10 around first gates 11. The embodiment never limits anydetail of the doping process.

As shown in FIG. 1E, remove second cover layer 14 and first cover layer13. Herein, because the details of the doping process are not limited,the distribution of doped impurities 15 also is not limited. FIG. 1Eonly shows a possible distribution of doped impurities 15: impurities 15only are doped into first gates 11.

Clearly, the embodiment performs the doping process after the patterningprocess for forming gates is finished, and then any defect induced bythe first-doping-then-patterning method is avoided. Further, because theembodiment forms two cover layers with different distribution after thepatterning process and before the doping process, the embodiment couldprecise details control which part is doped and the distribution ofimpurities.

Certainly, although the embodiment only uses two cover layers, thespirit of the invnetion is not limited by “two”. The embodiment could beexpanded to use several cover layers to precise the effect of the dopingprocess, where each cover layer has individual shape and individualdistribution.

Furthermore, if only first gates 11 need to be doped but any substrate10 around each of first gates 11 need not to be doped, the embodimentcould be amended to let first cover layer 11 only cover substrate 10around first gates 11 but not cover any first gate 11. Hence, thefollowing doping process could directly dopes impurities 15 into firstgates 11, effectively improve the conventional defects that it is hardto only dope partial gates but not dope both other gates and gate.

Meanwhile, the steps from FIG. 1C through FIG. 1E are amended as thesteps from FIG. 1F through FIG. 11:

As shown in FIG. 1F, treat first cover layer 13 with a treating processsuch that none of first gates 11 is covered by first cover layer 13.Herein, FIG. 1F shows the case that the thickness of first cover layer13 is globally reduced such that the treated first cover layer 13 isthinner than first gates 11. However, the embodiment does not limit thedetails of the treating process. It is possible to only remove partialfirst cover layer 13 on first gates 11, it also is possible to onlyreduce the thickness of partial first cover layer 13 over first gates 11but not reduce the thickness of other first cover layer 13.

As shown in FIG. 1G, covers partial substrate 10 by second cover layer14. Herein, second cover layer 14 is located over second gates 12 but isnot located over first gates 11.

As shown in FIG. 1H, perform a doping process. Herein, it is possible todope numerous impurities 15 only into first gates 11, it also ispossible to dope impurities 15 into both first gates 11 and partialsubstrate 10 around first gates 11. The embodiment never limits anydetail of the doping process.

As shown in FIG. 11, remove second cover layer 14 and first cover layer13. Herein, because the details of the doping process are not limited,the distribution of doped impurities 15 also is not limited. FIG. 1Eonly shows a possible distribution of doped impurities 15: impurities 15only are doped into first gates 11.

Additional, while the material of first cover layer 13 is a liquidmaterial, or any material could be firstly applied on substrate 10 as aliquid material and then be solidified, such as the photoresistmaterial, the treating process could be a spin-etch process with a etchrate not less than 500 angstroms/minute or a spin-etch process with aetch uniformity not larger than 10 percents, wherein the etch uniformityequals a ratio of a thickness difference between a maximum thickness anda minimum thickness of the liquid material and the maximum thickness ofthe liquid material, which at least has the following essential steps:

As shown in FIG. 1J, rotate substrate 10, first gates 11, second gates12, and first cover layer 13 around axis 16 of substrate 10. Herein,FIG. 1J only is a brief illustration, the embodiment never limits thegeometrical relation between axis 16 and first gates 11, second gates12, and first cover layer 13.

As shown in FIG. 1K, apply solvent 17 on first cover layer 13 to removepartial first cover layer 13.

Significantly, the spin-etch process is similar with the conventionspin-on glass or spin coating photoresist. The main difference is thatthe spin-etch process apply solvent 17 on first cover layer 17 androtate substrate 10 at the same time. Indisputably, by applying ofsolvent 17, the spin-etch process is more effective than theconventional spin-on glass or spin coating photoresist, and is moresuitable to form a thin layer while the material of the tin layer ishard to directly forms a thin film.

In general, suitable material of the spin-etch process at least hasresin, synthetic resin, photoresist, polymer, low dielectric constantdielectric material, and photoresist without acid. And suitable solventof the spin-etch process at least has developer, acid, and alkali.

Besides, the embodiment also could be amended as the following: firstlyrotate substrate 10 around axis 16 of substrate 10, and then forms coverfirst cover layer 13 (liquid material) on substrate 10. In other words,after the steps shown in FIG. 1A is finished, firstly rotates substrate10, next, forms first cover layer 13, and then performs the steps shownin FIG. 1F through FIG. 1K.

Besides, while the material of first cover layer 13 is photoresist orany photo-sensitive material, the treating process could be apart-expose process which at least has the following essential steps:

As shown in FIG. 1L, expose partial first cover layer 13. Herein, thenon-exposed first cover layer 13 is thinner than any first gate 11.

As shown in FIG. 1M, remove exposed first cover layer 131 such that eachfirst gate 11 is separated from other first gates 11 by non-exposedfirst cover layer 132.

Note that the part-expose process only expose the whole surface of firstcover layer 13 (photoresist layer), but not transfer any pattern intofirst cover layer 13 (photoresist layer).

Furthermore, both the spin-etch process and the part-expose process onlyare applied to plane first cover layer 11, especially to reduce thethickness of first cover layer 11, but is independent on other part ofthe embodiment. Hence, both the spin-etch process and the part-exposeprocess could be separated from other parts of the previous embodiment,and could be viewed as two preferred embodiments of the invnetion,especially two methods for forming the plane structure.

Another preferred embodiment is a method for forming a plane structure.As shown in FIG. 2, the embodiment at least has the following essentialsteps:

As shown in background block 21, provide a substrate.

As shown in liquid material block 22, form a liquid material on thesubstrate.

As shown in spin-etch block 23, rotate both the substrate and the liquidmaterial around an axis of the substrate and apply a solvent on theliquid material to remove partial liquid material simultaneously.

Herein, it is possible to form a pattern structure on the substratebefore the liquid material is formed. In the case, the pattern structureis thicker than the liquid material, and the spin-etch process is usedto reduce the thickness of the liquid material. Moreover, suitablematerial of the spin-etch process at least has resin, synthetic resin,photoresist, polymer, low dielectric constant dielectric material, andphotoresist without acid. And suitable solvent of the spin-etch processat least has developer, acid, and alkali. Moreover, solvent usually isdirectly applied on the axis of the substrate such that the solventuniformly distributed over the substrate.

The other preferred embodiment is a method for forming a planestructure. As shown in FIG. 3, the embodiment at least has the followingessential steps:

As shown in background block 31, provide a substrate.

As shown in photoresist block 32, form a photoresist layer on thesubstrate.

As shown in part-expose block 33, expose the surface part of thephotoresist layer is exposed.

As shown in removal block 34, remove exposed photoresist layer.

Similarly, it is possible to form a pattern structure on the substratebefore the photoresist layer is formed. In the case, the patternstructure is thicker than the liquid material.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for the purposeof illustration, various modifications may be made without deviatingfrom the spirit and scope of the invention. Accordingly, the inventionis not limited except as by the appended claims.

1-8. (canceled)
 9. A method for forming a plane structure, comprising:providing a substrate; forming a liquid material on said substrate; andtreating said liquid material by a spin-etch process with a etchuniformity not larger than 10 percents, wherein said etch uniformityequals a ratio of a thickness difference between a maximum thickness anda minimum thickness of said liquid material and said maximum thicknessof said liquid material.
 10. The method of claim 9, a pattern structurebeing formed on said substrate before said liquid material is formed.11. The method of claim 10, said pattern structure being thicker thansaid liquid material.
 12. The method of claim 9, said spin-etch processrotating both said substrate and said liquid material around an axis ofsaid substrate and applying a solvent on said liquid material to removepartial said liquid material simultaneously.
 13. The method of claim 9,said liquid material being chosen from the group consisting of thefollowing: resin, synthetic resin, photoresist, polymer, low dielectricconstant dielectric material, and photoresist without acid.
 14. Themethod of claim 9, said solvent being chosen from the group consistingof the following: developer, acid, and alkali.
 15. The method of claim9, further comprising the step of rotating said substrate around saidaxis before said liquid is formed on said substrate.
 16. The method ofclaim 9, said solvent being directly applied on said axis of saidsubstrate during said spin-etch process.